/* URL to the PHP page called for receiving suggestions for a keyword*/
var getFunctionsUrl = "suggest.php?keyword=";
/* URL for seeing the results for the selected suggestion */
var phpHelpUrl = "http://www.php.net/manual/en/function.";
/* the keyword for which an HTTP request has been initiated */
var httpRequestKeyword = "";
/* the last keyword for which suggests have been requested */
var userKeyword = "";
/* number of suggestions received as results for the keyword */
var suggestions = 0;
/* the maximum number of characters to be displayed for a suggestion */
var suggestionMaxLength = 30;
/* flag that indicates if the up or down arrow keys were pressed
 the last time a keyup event occurred  */
var isKeyUpDownPressed = false;
/* the last suggestion that has been used for autocompleting the keyword */
var autocompletedKeyword = "";
/* flag that indicates if there are results for the current requested keyword*/
var hasResults = false;
/* the identifier used to cancel the evaluation with the clearTimeout method. */
var timeoutId = -1;
/* the currently selected suggestion (by arrow keys or mouse)*/
var position = -1;
/* cache object containing the retrieved suggestions for different keywords */
var oCache = new Object();
/* the minimum and maximum position of the visible suggestions */
var minVisiblePosition = 0;
var maxVisiblePosition = 9;
// when set to true, display detailed error messages
var debugMode = true;
/* the XMLHttp object for communicating with the server */
var xmlHttpGetSuggestions = createXmlHttpRequestObject();
/* the onload event is handled by our init function */
window.onload = init;

// creates an XMLHttpRequest instance
function createXmlHttpRequestObject() {
	// will store the reference to the XMLHttpRequest object
	var xmlHttp;
	// this should work for all browsers except IE6 and older
	try {
		// try to create XMLHttpRequest object
		xmlHttp = new XMLHttpRequest();
	} catch (e) {
		// assume IE6 or older
		var XmlHttpVersions = new Array("MSXML2.XMLHTTP.6.0",
				"MSXML2.XMLHTTP.5.0", "MSXML2.XMLHTTP.4.0",
				"MSXML2.XMLHTTP.3.0", "MSXML2.XMLHTTP", "Microsoft.XMLHTTP");
		// try every prog id until one works
		for ( var i = 0; i < XmlHttpVersions.length && !xmlHttp; i++) {
			try

			{
				// try to create XMLHttpRequest object
				xmlHttp = new ActiveXObject(XmlHttpVersions[i]);
			} catch (e) {
			}
		}
	}
	// return the created object or display an error message
	if (!xmlHttp)
		alert("Error creating the XMLHttpRequest object.");
	else
		return xmlHttp;
}

/* function that initializes the page */
function init() {
	// retrieve the input control for the keyword
	var oKeyword = document.getElementById("keyword");
	// prevent browser from starting the autofill function
	oKeyword.setAttribute("autocomplete", "off");
	// reset the content of the keyword and set the focus on it
	oKeyword.value = "";
	oKeyword.focus();
	// set the timeout for checking updates in the keyword's value
	setTimeout("checkForChanges()", 500);
}

/* function that adds to a keyword an array of values */
function addToCache(keyword, values) {
	// create a new array entry in the cache
	oCache[keyword] = new Array();
	// add all the values to the keyword's entry in the cache
	for (i = 0; i < values.length; i++)
		oCache[keyword][i] = values[i];
}

/* 
 function that checks to see if the keyword specified as parameter is in 
 the cache or tries to find the longest matching prefixes in the cache 
 and adds them in the cache for the current keyword parameter
 */
function checkCache(keyword) {
	// check to see if the keyword is already in the cache
	if (oCache[keyword])
		return true;
	// try to find the biggest prefixes
	for (i = keyword.length - 2; i >= 0; i--) {
		// compute the current prefix keyword 
		var currentKeyword = keyword.substring(0, i + 1);
		// check to see if we have the current prefix keyword in the cache
		if (oCache[currentKeyword]) {
			// the current keyword's results already in the cache
			var cacheResults = oCache[currentKeyword];
			// the results matching the keyword in the current cache results
			var keywordResults = new Array();
			var keywordResultsSize = 0;
			// try to find all matching results starting with the current prefix
			for (j = 0; j < cacheResults.length; j++) {

				if (cacheResults[j].indexOf(keyword) == 0)
					keywordResults[keywordResultsSize++] = cacheResults[j];
			}
			// add all the keyword's prefix results to the cache
			addToCache(keyword, keywordResults);
			return true;
		}
	}
	// no match found
	return false;
}

/* initiate HTTP request to retrieve suggestions for the current keyword */
function getSuggestions(keyword) {
	/* continue if keyword isn't null and the last pressed key wasn't up or 
	   down */
	if (keyword != "" && !isKeyUpDownPressed) {
		// check to see if the keyword is in the cache
		isInCache = checkCache(keyword);
		// if keyword is in cache...
		if (isInCache == true) {
			// retrieve the results from the cache          
			httpRequestKeyword = keyword;
			userKeyword = keyword;
			// display the results in the cache
			displayResults(keyword, oCache[keyword]);
		}
		// if the keyword isn't in cache, make an HTTP request
		else {
			if (xmlHttpGetSuggestions) {
				try {
					/* if the XMLHttpRequest object isn't busy with a previous
					   request... */
					if (xmlHttpGetSuggestions.readyState == 4
							|| xmlHttpGetSuggestions.readyState == 0) {
						httpRequestKeyword = keyword;
						userKeyword = keyword;
						xmlHttpGetSuggestions.open("GET", getFunctionsUrl
								+ encode(keyword), true);
						xmlHttpGetSuggestions.onreadystatechange = handleGettingSuggestions;
						xmlHttpGetSuggestions.send(null);
					}
					// if the XMLHttpRequest object is busy...
					else {
						// retain the keyword the user wanted             
						userKeyword = keyword;
						// clear any previous timeouts already set
						if (timeoutId != -1)
							clearTimeout(timeoutId);
						// try again in 0.5 seconds     
						timeoutId = setTimeout("getSuggestions(userKeyword);",
								500);
					}
				} catch (e)

				{
					displayError("Can't connect to server:\n" + e.toString());
				}
			}
		}
	}
}

/* transforms all the children of an xml node into an array */
function xmlToArray(resultsXml) {
	// initiate the resultsArray
	var resultsArray = new Array();
	// loop through all the xml nodes retrieving the content  
	for (i = 0; i < resultsXml.length; i++)
		resultsArray[i] = resultsXml.item(i).firstChild.data;
	// return the node's content as an array
	return resultsArray;
}

/* handles the server's response containing the suggestions 
 for the requested keyword  */
function handleGettingSuggestions() {
	//if the process is completed, decide what to do with the returned data
	if (xmlHttpGetSuggestions.readyState == 4) {
		// only if HTTP status is "OK"
		if (xmlHttpGetSuggestions.status == 200) {
			try {
				// process the server's response
				updateSuggestions();
			} catch (e) {
				// display the error message
				displayError(e.toString());
			}
		} else {
			displayError("There was a problem retrieving the data:\n"
					+ xmlHttpGetSuggestions.statusText);
		}
	}
}

/* function that processes the server's response */
function updateSuggestions() {
	// retrieve the server's response 
	var response = xmlHttpGetSuggestions.responseText;
	// server error?
	if (response.indexOf("ERRNO") >= 0 || response.indexOf("error:") >= 0
			|| response.length == 0)
		throw (response.length == 0 ? "Void server response." : response);
	// retrieve the document element
	response = xmlHttpGetSuggestions.responseXML.documentElement;
	// initialize the new array of functions' names
	nameArray = new Array();
	// check to see if we have any results for the searched keyword

	if (response.childNodes.length) {
		/* we retrieve the new functions' names from the document element as 
		   an array */
		nameArray = xmlToArray(response.getElementsByTagName("name"));
	}
	// check to see if other keywords are already being searched for
	if (httpRequestKeyword == userKeyword) {
		// display the results array
		displayResults(httpRequestKeyword, nameArray);
	} else {
		// add the results to the cache
		// we don't need to display the results since they are no longer useful
		addToCache(httpRequestKeyword, nameArray);
	}
}

/* populates the list with the current suggestions */
function displayResults(keyword, results_array) {
	// start building the HTML table containing the results  
	var div = "<table>";
	// if the searched for keyword is not in the cache then add it to the cache
	if (!oCache[keyword] && keyword)
		addToCache(keyword, results_array);
	// if the array of results is empty display a message
	if (results_array.length == 0) {
		div += "<tr><td>No results found for <strong>" + keyword
				+ "</strong></td></tr>";
		// set the flag indicating that no results have been found 
		// and reset the counter for results
		hasResults = false;
		suggestions = 0;
	}
	// display the results
	else {
		// resets the index of the currently selected suggestion
		position = -1;
		// resets the flag indicating whether the up or down key has been pressed
		isKeyUpDownPressed = false;
		/* sets the flag indicating that there are results for the searched 
		   for keyword */
		hasResults = true;
		// get the number of results from the cache
		suggestions = oCache[keyword].length;
		// loop through all the results and generate the HTML list of results
		for ( var i = 0; i < oCache[keyword].length; i++) {
			// retrieve the current function
			crtFunction = oCache[keyword][i];
			// set the string link for the for the current function 
			// to the name of the function
			crtFunctionLink = crtFunction;
			// replace the _ with - in the string link
			while (crtFunctionLink.indexOf("_") != -1)
				crtFunctionLink = crtFunctionLink.replace("_", "-");
			// start building the HTML row that contains the link to the 
			// PHP help page of the current function

			div += "<tr id='tr" + i
					+ "' onclick='location.href=document.getElementById(\"a"
					+ i + "\").href;' onmouseover='handleOnMouseOver(this);' "
					+ "onmouseout='handleOnMouseOut(this);'>"
					+ "<td align='left'><a id='a" + i + "' href='" + phpHelpUrl
					+ crtFunctionLink + ".php";
			// check to see if the current function name length exceeds the maximum 
			// number of characters that can be displayed for a function name
			if (crtFunction.length <= suggestionMaxLength) {
				// bold the matching prefix of the function name and of the keyword
				div += "'><b>"
						+ crtFunction.substring(0, httpRequestKeyword.length)
						+ "</b>"
				div += crtFunction.substring(httpRequestKeyword.length,
						crtFunction.length)
						+ "</a></td></tr>";
			} else {
				// check to see if the length of the current keyword exceeds 
				// the maximum number of characters that can be displayed
				if (httpRequestKeyword.length < suggestionMaxLength) {
					/* bold the matching prefix of the function name and that of the 
					   keyword */
					div += "'><b>"
							+ crtFunction.substring(0,
									httpRequestKeyword.length) + "</b>"
					div += crtFunction.substring(httpRequestKeyword.length,
							suggestionMaxLength)
							+ "</a></td></tr>";
				} else {
					// bold the entire function name
					div += "'><b>"
							+ crtFunction.substring(0, suggestionMaxLength)
							+ "</b></td></tr>"
				}
			}
		}
	}
	// end building the HTML table
	div += "</table>";
	// retrieve the suggest and scroll object
	var oSuggest = document.getElementById("suggest");
	var oScroll = document.getElementById("scroll");
	// scroll to the top of the list
	oScroll.scrollTop = 0;
	// update the suggestions list and make it visible
	oSuggest.innerHTML = div;
	oScroll.style.visibility = "visible";
	// if we had results we apply the type ahead for the current keyword
	if (results_array.length > 0)
		autocompleteKeyword();
}

/* function that periodically checks to see if the typed keyword has changed */
function checkForChanges() {
	// retrieve the keyword object

	var keyword = document.getElementById("keyword").value;
	// check to see if the keyword is empty
	if (keyword == "") {
		// hide the suggestions
		hideSuggestions();
		// reset the keywords 
		userKeyword = "";
		httpRequestKeyword = "";
	}
	// set the timer for a new check 
	setTimeout("checkForChanges()", 500);
	// check to see if there are any changes
	if ((userKeyword != keyword) && (autocompletedKeyword != keyword)
			&& (!isKeyUpDownPressed))
		// update the suggestions
		getSuggestions(keyword);
}

/* function that handles the keys that are pressed */
function handleKeyUp(e) {
	// get the event
	e = (!e) ? window.event : e;
	// get the event's target
	target = (!e.target) ? e.srcElement : e.target;
	if (target.nodeType == 3)
		target = target.parentNode;
	// get the character code of the pressed button
	code = (e.charCode) ? e.charCode : ((e.keyCode) ? e.keyCode
			: ((e.which) ? e.which : 0));
	// check to see if the event was keyup
	if (e.type == "keyup") {
		isKeyUpDownPressed = false;
		// check to see we if are interested in the current character
		if ((code < 13 && code != 8) || (code >= 14 && code < 32)
				|| (code >= 33 && code <= 46 && code != 38 && code != 40)
				|| (code >= 112 && code <= 123)) {
			// simply ignore non-interesting characters
		} else
		/* if Enter is pressed we jump to the PHP help page of the current 
		   function */
		if (code == 13) {
			// check to see if any function is currently selected
			if (position >= 0) {
				location.href = document.getElementById("a" + position).href;
			}
		} else
		// if the down arrow is pressed we go to the next suggestion
		if (code == 40) {
			newTR = document.getElementById("tr" + (++position));
			oldTR = document.getElementById("tr" + (--position));
			// deselect the old selected suggestion   
			if (position >= 0 && position < suggestions - 1)
				oldTR.className = "";

			// select the new suggestion and update the keyword
			if (position < suggestions - 1) {
				newTR.className = "highlightrow";
				updateKeywordValue(newTR);
				position++;
			}
			e.cancelBubble = true;
			e.returnValue = false;
			isKeyUpDownPressed = true;
			// scroll down if the current window is no longer valid
			if (position > maxVisiblePosition) {
				oScroll = document.getElementById("scroll");
				oScroll.scrollTop += 18;
				maxVisiblePosition += 1;
				minVisiblePosition += 1;
			}
		} else
		// if the up arrow is pressed we go to the previous suggestion
		if (code == 38) {
			newTR = document.getElementById("tr" + (--position));
			oldTR = document.getElementById("tr" + (++position));
			// deselect the old selected position
			if (position >= 0 && position <= suggestions - 1) {
				oldTR.className = "";
			}
			// select the new suggestion and update the keyword
			if (position > 0) {
				newTR.className = "highlightrow";
				updateKeywordValue(newTR);
				position--;
				// scroll up if the current window is no longer valid
				if (position < minVisiblePosition) {
					oScroll = document.getElementById("scroll");
					oScroll.scrollTop -= 18;
					maxVisiblePosition -= 1;
					minVisiblePosition -= 1;
				}
			} else if (position == 0)
				position--;
			e.cancelBubble = true;
			e.returnValue = false;
			isKeyUpDownPressed = true;
		}
	}
}

/* function that updates the keyword value with the value 
 of the currently selected suggestion */
function updateKeywordValue(oTr) {
	// retrieve the keyword object
	var oKeyword = document.getElementById("keyword");
	// retrieve the link for the current function
	var crtLink = document.getElementById(
			"a" + oTr.id.substring(2, oTr.id.length)).toString();
	// replace - with _ and leave out the .php extension

	crtLink = crtLink.replace("-", "_");
	crtLink = crtLink.substring(0, crtLink.length - 4);
	// update the keyword's value
	oKeyword.value = unescape(crtLink.substring(phpHelpUrl.length,
			crtLink.length));
}

/* function that removes the style from all suggestions*/
function deselectAll() {
	for (i = 0; i < suggestions; i++) {
		var oCrtTr = document.getElementById("tr" + i);
		oCrtTr.className = "";
	}
}

/* function that handles the mouse entering over a suggestion's area 
 event */
function handleOnMouseOver(oTr) {
	deselectAll();
	oTr.className = "highlightrow";
	position = oTr.id.substring(2, oTr.id.length);
}

/* function that handles the mouse exiting a suggestion's area event */
function handleOnMouseOut(oTr) {
	oTr.className = "";
	position = -1;
}

/* function that escapes a string */
function encode(uri) {
	if (encodeURIComponent) {
		return encodeURIComponent(uri);
	}

	if (escape) {
		return escape(uri);
	}
}

/* function that hides the layer containing the suggestions */
function hideSuggestions() {
	var oScroll = document.getElementById("scroll");
	oScroll.style.visibility = "hidden";
}

/* function that selects a range in the text object passed as parameter */
function selectRange(oText, start, length) {
	// check to see if in IE or FF
	if (oText.createTextRange) {
		//IE
		var oRange = oText.createTextRange();
		oRange.moveStart("character", start);
		oRange.moveEnd("character", length - oText.value.length);
		oRange.select();

	} else
	// FF
	if (oText.setSelectionRange) {
		oText.setSelectionRange(start, length);
	}
	oText.focus();
}

/* function that autocompletes the typed keyword*/
function autocompleteKeyword() {
	//retrieve the keyword object
	var oKeyword = document.getElementById("keyword");
	// reset the position of the selected suggestion
	position = 0;
	// deselect all suggestions
	deselectAll();
	// highlight the selected suggestion 
	document.getElementById("tr0").className = "highlightrow";
	// update the keyword's value with the suggestion
	updateKeywordValue(document.getElementById("tr0"));
	// apply the type-ahead style
	selectRange(oKeyword, httpRequestKeyword.length, oKeyword.value.length);
	// set the autocompleted word to the keyword's value
	autocompletedKeyword = oKeyword.value;
}

/* function that displays an error message */
function displayError(message) {
	// display error message, with more technical details if debugMode is true
	alert("Error accessing the server! " + (debugMode ? "\n" + message : ""));
}
